In conventional motor vehicles, a steering movement of a vehicle wheel is realized with a pivoted steering knuckle (“corner”) that forms part of the wheel suspension. In this case, a wheel bearing unit fixed on the steering knuckle serves for mounting the vehicle wheel. Toward the center of the vehicle, the steering knuckle is mounted on the chassis, particularly on a subframe, by means of wheel guiding elements (“control arms”). It is common practice to define pivot points for the steering knuckle with upper and lower control arms that engage on the steering knuckle. The connecting line between the two pivot points forms the usually oblique pivoting axis for the pivoting motion of the steering knuckle. In order to pivot the steering knuckle and thusly turn a wheel mounted on the steering knuckle, it is possible, for example, to provide a steering arm (knuckle arm) that engages on the steering knuckle and to which the steering forces are transmitted, for example, by means of A-arms. Due to its pivoting function for the wheel mounted on the steering knuckle, the steering knuckle frequently is simply referred to as a pivot bearing of the wheel.
In addition to transmitting the steering movement to the mounted wheel, the steering knuckle also needs to absorb the forces applied to the wheel because not only the weight of the vehicle, but practically all forces for the longitudinal and lateral deceleration of the vehicle are applied to the steering knuckle such that the steering knuckle needs to be realized in a correspondingly stable fashion.
The moving direction of the wheel mounted on the steering knuckle therefore can be defined by means of the steering knuckle. When driving straight ahead, the moving direction of the wheels should ideally be parallel to the longitudinal axis of the vehicle at all times, but this is frequently not the case, for example, because the front wheels of a front-wheel drive vehicle are usually pressed inward (“toe-in”) when the vehicle accelerates due to elastic deformations in components of the wheel suspension. During an ideal cornering maneuver or so-called neutral handling, all wheels are exactly turned in such a way that the ideal toe angle is adjusted. At a certain curve radius and a certain speed, this ideal wheel position should make it possible to build up a cornering force in the tire that is proportional to the normal force of the respective wheel. Referred to the axle, this means that the cornering forces need to build up in accordance with the axial load ratio. If this is not the case, oversteering or understeering will occur.
In torsion beam rear axles, in particular, in which the control arms are connected by a cross arm in order to improve the handling, it is known that the wheels have a tendency to oversteer while cornering such that, in contrast to ideal cornering, all wheels of the vehicle are no longer optimally positioned for this type of cornering. This may have the undesirable consequence that the rear end of the vehicle breaks away more easily while cornering.
In order to solve, in particular, the aforementioned problem of torsion beam rear axles, it was already considered to realize an active adjustment of the steering knuckles that carry the wheels, namely by means of an actuator. The technical realization of such an active adjustment of the steering knuckle, however, requires significant constructive expenditures because the respective steering knuckles usually need to be provided with two bearing points with bushings in order to achieve a rotatory degree of freedom. In addition, corresponding thrust washers or axial bearings need to be provided perpendicular thereto in order to transmit the forces for pivoting the steering knuckle. Such bearing points should furthermore be free of play and smooth-moving, as well as sealed against water and environmental influences, and also have a suitable rigidity in order to fulfill the specifications with respect to the properties of the chassis. In addition, it is necessary to provide a steering arm, to which the actuator is coupled.
Other known systems designed for solving this problem are configured for special axle systems and either not suitable for other axle systems or do not define the steering axle satisfactorily.
In view of the foregoing, at least one objective is to develop a steering knuckle that makes it possible to adjust the moving direction of the vehicle wheel in the desired fashion, for example, in order to counteract the oversteering of torsion beam rear axles. In addition, other objectives, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.